If you circuit uses a Single transformer , try one of these
http://www.ebay.co.uk/itm/LED-Driver-Transformer-DC-12v-6w-12w-18w-30w-50w-for-MR11-MR16-LED-Strip-/400613130595?pt=UK_Home_Garden_Night_Lights_Fairy_Lights&var=&hash=item5d46674163
I would get a 50w for 5x 6.5w LEDs , will give...